1. Field of the Invention
This invention pertains to lifting devices and more particularly to apparatus for raising heavy objects a short distance above a horizontal surface.
2. Description of the Prior Art
It is a common practice in the arc welding industry to mount a welding power supply to a running gear. The running gear enables the welding power supply to be transported with ease to different jobs in an area. The running gears are normally steerable, which aids in maneuvering them to the desired locations.
It is further well known to carry one or more large cylinders of inert arc-shielding gases on the running gears. The gas cylinders are very heavy, often weighing as much as 180 pounds. The gas inside the cylinders is under very high pressure, as, for example, 2,000 pounds per square inch. At the top of the cylinder is a valve, which is protected by a removable cover. The gas cylinders are normally supported on a sturdy horizontal pan on the back end of the running gear. The pan is located a few inches above the floor. In that manner, the welding power supply and the gas cylinders are transportable together by the running gear.
It has long been a major problem to load the gas cylinders onto and unload them from the running gear pan. Overhead cranes are rarely available at the cylinder storage area. Consequently, the usual loading and unloading method has been to manually lift the cylinders. A person hugs a cylinder, wrapping his arms around it, and lifts it by using his back and/or legs. Another prior solution has been to tip the cylinder away from the running gear pan such that the cylinder bottom surface is in contact with the edge of the pan. The cylinder is then tilted to the upright position, partially supported on the pan, and the cylinder is slid fully onto the pan.
Both prior solutions are far from satisfactory. Direct lifting has the potential for causing serious injury to the person. Tilting the cylinder presents the risk of the cylinder slipping and striking a fixed structure with the valve cover or the valve itself. Damage to the valve creates a danger because of the high gas pressure inside the cylinder.
In a few situations, it may be possible to tip the running gear such that the edge of the pan is on or close to the floor, and then tip and slide the cylinder up onto the pan. However, that solution is impractical for the great majority of cases.
Thus, a need exists for a way to safely load gas cylinders onto and unload them from welding power supply running gears.